


Why Knot?

by peonylanterns



Category: Undertale (Video Game)
Genre: Biting, F/M, Female Reader, Fingering, Knotting, Long Orgasms, Smut, cum kink, excessive cum
Language: English
Status: Completed
Published: 2016-07-06
Updated: 2016-07-06
Packaged: 2018-07-21 19:32:57
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,345
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/7400989
Author URL: https://archiveofourown.org/users/peonylanterns/pseuds/peonylanterns
Summary: <blockquote class="userstuff">
              <p>In which a conversation about Seinfeld leads to messy, drawn-out sex. Includes knotting.</p><p>Critique heavily encouraged.</p>
            </blockquote>





	Why Knot?

**Author's Note:**

  * For [Milkynubs](https://archiveofourown.org/users/Milkynubs/gifts).
  * Inspired by [A Universe in Which Cumming is Ten Times More Tedious (AKA Undertable)](https://archiveofourown.org/works/6724621) by [Milkynubs](https://archiveofourown.org/users/Milkynubs/pseuds/Milkynubs). 



“Yeah, but they stopped at season nine.”

“seriously? only nine seasons?” Sans gestures at his television screen, which shows three men using an oversized dresser as a bunk bed. “you humans manage to churn out fifteen seasons of absolute bullshit, but you’ve got only nine seasons of seinfeld?”

You narrow your eyes at him. “And how many seasons of MTT do monsters have? Last time I checked, it was something like twenty-three.”

“that’s different. down here - ”

“Ten new episodes a week! Half of them featuring a tin can swooning onto a bed of rose petals!” At this, you press your hand to your forehead and throw your body across his lap, feigning sudden weakness, “Mood lighting! A live orchestra! Pyrotechnics! And absolutely no plot to speak of!”

“you say that, but i’ve seen you watching it with papyrus. you get just as excited as he does.”

You blush. “Well, that’s only because it's so hilariously _bad_.”

“really? you sure you don't have a crush on mettaton, too?” His hand creeps up the side of your thigh to stroke at your hipbone. “you don't wanna kiss his calculator-screen face?” Sans puts a hand under your back and hauls you up so he can press his teeth against your cheek.

“Nah. I think I prefer skeletons.”

He laughs. You don’t notice that he’s put his hand up your shirt until he unclasps your bra and says, “wanna prove it to me?”

“Yeah.” You take off your top, tossing it onto the sofa’s arm. “I think I can do that.”

Before you can wriggle out of your shorts, he’s pressed his hand against the denim crease between your legs. Sans traces the seam in the fabric, rubbing against your slit through the thick cloth. You let yourself fall into him, head against his shoulder and legs spread across his lap.

“bet you're wet for me already,” he says softly, and slips his fingers into your underwear to check. The segmented bone slides slickly through your folds as it dips inside you, swiping up the clear, sticky dew of your arousal. He brings his fingers to his mouth, licks them, then slowly eases them back inside you - deeper this time, with slow and gentle motions and until you whimper out his name.

“That’s good, that’s so good...” You shift in his lap, angling your hips to grind your clit against his palm. The smooth friction of him sparks a very familiar warmth through your belly, and you sigh contentedly, wrapping your arms him. “Sans, you’re gonna make me come...Sans, _Sans_ \-- what -- why’d you stop?”

“let me fuck you.” Sans’ voice is strained. He ruts his pelvis against the back of your thighs, and you can feel his erection through the thick cotton of his sweatpants. “please.”

As he speaks he pulls his shirt off, then pulls your shorts and underwear down your legs, letting the clothes fall into a haphazard heap on the floor. You let him wrap your thighs around his hips, his movements rough, almost desperate. He yanks down his waistband to free his cock, already swollen and slick with precome, and you climb on top of him. Teasingly, with a slight roll of your hips, you glide your slit against his shaft before you mount him, sinking him inside little by little to let your body adjust to the size of him.

Sans grips you so hard that the bones of his hands leave white imprints. He can feel your arousal dripping down his length as he penetrates you, the creamy heat of your core pulling him deeper with every one of your fluttery gasps. When he finally hilts inside you, pressing the head of his cock against the soft center of your body, you let out a weak little moan that nearly makes him lose control of himself.

The tips of his phalanges dig into your back as he clasps you tighter. He breathes your name into the crook of your neck, and the sound travels like a shiver down your spine, raising goosebumps on your skin. Too far gone for words, you respond with a hoarse little cry. Clutching at the back of his spine, tightening around him as he replies with a sharp nip to your collarbone, you lay limply against his ribcage as he starts fucking you.

His strokes are maddeningly slow, pressing deep and withdrawing shallowly before he fits himself into you again, as if his body can’t bear to stay parted from your own. Sans closes his eyes and all he feels is the sensation of your melting warmth, the taste of your mouth as he kisses you, the sensuous velvet of your skin pressed against bone. Your fingers are hooked in his ribs, clinging to him like he’s the only thing keeping you afloat, and he’s so close, he’s already so fucking close to spilling his load that he has to force himself not to give in.

You can feel the slight stretch of his knot starting to swell inside of you, a tight pressure that aches and pulses as he ties with you, and you cry out as it locks you against him. “Sans,” you whimper, “Oh god, _Sans_.”

He pulls you into him, holding you tight as you pant out in time with his thrusts, brushing his mouth against your forehead when he feels you tensing up around him, but soon he’s fucking you with hard and sloppy strokes, slamming his pelvis against your hips and groaning his need. The urgency of his lovemaking sends ripples of heat through you, and when you come for him it’s like an unfurling of golden silk through your body, fluid and sweet, hazy and clouded with incoherent desire.

When he feels the clench of your orgasm, a violent and sudden impulse rises in his chest to mark you, claim you, make you his own. Before he can stop himself he’s sinking his teeth into the space between your neck and shoulder, biting down hard enough that you shudder against him. And then he’s coming too, cock jerking hard as he fills you with his seed, throbbing as it floods you with wave after wave of liquid warmth.

He’s murmuring mindlessly in your ear, slurring his words because he’s so lost in his own pleasure, telling you how good it feels to be inside you like this, how fucking beautiful you look taking his knot, how much he loves y--, uh, how much he loves the way you make him _feel_ and how he wants to fuck you until neither of you has the strength to go on - but you’re more focused on how intensely you can feel every pulse, every spurt of thick monster come that he’s pumping into you. And though he’s still thrusting, he’s slowed his pace to a slow rhythm that’s just enough to tip you over the edge again. Your eyelids flutter as you hold him tighter inside yourself, your mind blurs into a pastel mist, and you’re just barely aware of the liquid dripping out from along the knot and running down your thighs.

After a few minutes, his orgasm finally subsides to a trickle. You’re lying with your head against his sternum, eyes dreamy and the beginnings of a bruise darkening on your neck, shivering in pleasure when an especially intense throb of come nudges you back into arousal. Sans is still breathing hard, arms wrapped loosely around your back, face buried in your shoulder as he tries to calm himself down.

“you alright?”

You nod weakly. It takes almost all your strength to do so.

Sans laughs. “good,” he says, and pats you on the head. He settles against the couch, leaning into the cushions as he shifts the two of you into a more comfortable position.

“So,” you manage to say, “About Seinfeld. There’s only nine seasons, but the producer made a new show called ‘Curb Your Enthusiasm’.”

“yeah?”

“I think you’d like it.” you yawn, “I’ll see if I can scrounge a dvd of it from Alphy’s non-anime collection tomorrow.”

**Author's Note:**

> If you liked this, please let me know what appealed to you. If you didn't like this, please leave a comment telling me what to improve on. Thanks!
> 
> Feel free to contact me at: peonylanterns.tumblr.com


End file.
